1. Technical Field
The present invention relates to an oscillation circuit, an oscillator, a manufacturing method of an oscillator, an electronic device, and a moving object.
2. Related Art
For a resonator such as a crystal resonator (piezoelectric resonator) or a resonator having a micro electromechanical systems (MEMS), it is necessary to inspect characteristics of the resonator by performing overdrive inspection by inspecting frequency characteristics of the resonator by applying an AC signal with high current, voltage, or power to drive the resonator, or drive level inspection by inspecting fluctuation of frequency characteristics of the resonator by applying a signal obtained by gradually increasing or decreasing a frequency of an AC signal with high current, voltage, or power to drive the resonator.
Meanwhile, an oscillator in which a crystal resonator and an oscillation circuit are accommodated in the same accommodation container has been developed, in order to provide a miniaturized oscillator. Accordingly, various investigations are performed in order to inspect characteristics of the resonator, after mounting the crystal resonator and the oscillation circuit in the same accommodation container.
JP-A-2001-102870 discloses a crystal oscillator that includes an analog switch which is controlled by applying a specified DC voltage to an inspecting terminal dedicated to inspection used when inspecting characteristics of a crystal resonator and a power input terminal, in which the crystal resonator is electrically connected to the inspecting terminal through the analog switch when inspecting the crystal resonator, and the inspecting terminal is separated from the crystal resonator when normally operating the oscillator.
In addition, JP-A-2009-201097 discloses a crystal oscillator which uses a function terminal of the oscillator as an inspecting terminal of a crystal resonator.
In JP-A-2009-201097, the inspecting terminal of the crystal resonator is commonly used as an output terminal and a standby terminal of the crystal oscillator, and accordingly it is possible to miniaturize the oscillator compared to a configuration of including the dedicated inspecting terminal as disclosed in JP-A-2001-102870.
In JP-A-2009-201097, the output terminal and the standby terminal are selected as terminals to be used with the inspecting terminal of the crystal resonator, and this is because a switching circuit is controlled with a power supply voltage when inspecting characteristics of the crystal resonator.
It is necessary to apply a potential with high stability to a power supply terminal and an earth terminal, in order to stabilize an operation of the switching circuit. If such terminals are used as the crystal inspection terminal, a signal of the crystal resonator may be superposed with a DC voltage, and accordingly the power supply voltage may be unstable. Therefore, the two terminals of the crystal resonator are limited to the output terminal and the standby terminal.
In both JP-A-2001-102870 and JP-A-2009-201097, when performing the inspection of the resonator, the power supply terminal and the earth terminal are necessary for controlling the analog switch and the switching circuit, in addition to two crystal inspection terminals which are connected to the resonator, and thus, it is necessary to manage the connection of electrodes and probes electrically connected to the four terminals. As there are a great number of connection portions to be managed, a possibility of occurrence of inspection malfunction due to connection failure increases, and reliability in the inspection of the resonator may be decreased.